This cool passage from David Metz’ book The Limits to Travel was posted on Tom Vanderbilt’s How We Drive blog (emphasis added):
All in all, the available evidence supports the idea that man has evolved to travel long distances by both walking and running. As man developed technologies, these could be exploited to travel farther and faster. Thus the origins of much of the history and geography of mankind that we learnt in school, not least the willingness of people to migrate from where they were born to other cities or strange new countries in search of a better life. This has had implications for our own evolution. Steve Jones, professor of genetics at University College London (UCL), has pointed out that if one’s ancestors came from the same village they may well have been related, but this is much less likely if they were born hundreds of miles apart. In 19th-century Oxfordshire, the average distance between birthplaces of marriage partners was less than ten miles. Now it is more than 50, and in the US it is several hundred. A consequence of this increasing mobility is that the world’s populations are beginning to merge genetically. Steve Jones suggests that the most important event in recent human evolution has been the invention of the bicycle.